Composition of matter for selectively controlling metal pickling baths



UNITED STATES PATEN'll OFFICE COMPOSITION OF MATTER FOR SELEC- TIVELY CONTROLLING lVIETAL PICKLING BATHS James H. Gravell, Elkins Park, Pa.

No Drawing.

Application April 2, 1931 Serial No. 527,350

4 Claims.

This invention relates to the art of metal pickling and is specifically directed to a new embodiment of a composition of matter for selectively controlling a metal pickling bath.

It is the custom to introduce into a metal pickling bath, which usually consists of a dilute acid solution, various chemicals for improving the action of the said bath. These added materials may be generally classed as (A) selective controlling agents which inhibit the action of the acid bath on good metal, (B) materials, usually of a colloidal nature, which produce a foam on top of the metal pickling bath for filtering the moisture out of the escaping gases thereby eliminating fumes arising from the same and (C) materials which assist the acid of the bath in actually cleaning the metal, known as auxiliary cleaning agents.

Sometimes these various agents are added in liquid form but it has been found through experience, that it is more satisfactory to use them in the solid state.

My experience has shown that, generally stated, the finer the solids are pulverized the more effective they become and hence it has heretofore been my practice to introduce solid agents in the form of extremely fine powders. Difficulty, however, has been encountered in that powdered materials tend to float on the surface of the bath and are often withdrawn on the metal in its removal after pickling and hence lost. This is particularly true when foaming agents are used, for although the specific gravity of the powdered material is greater than that of the pickling bath, the surface tension of the bath prevents the material from sinking.

I have discovered that the objection to the floating of the inhibiting material may be overcome by aggregating the fine particles of the various agents into compressed or compacted bodies of the aggregates, such as blocks, pellets, capsules or briquettes, the density being increased so that the agents will quickly sink in the bath. It has been found, however, that such bodies disintegrate or such aggregated units of the materials dissolve or fall apart in the pickling bath so slowly that uncertainty as to the content of the bath results or much time is lost in waiting for the full beneficial results.

The object of this invention is to provide a solid aggregate of matter of a density to sink in metal pickling baths and which will be quickly disintegrated by the action of the said bath.

Other objects of this invention are to provide means of accurately doling out the agents, to

increase the effectiveness of the agents and generally to improve the art of metal pickling.

Generally stated, the invention consists of an effervescent solid aggregate of compressed or compacted particles of matter of sufficient density and weight to sink in the metal pickling bath and which comprises a pickling agent. The aggregating and compacting may be accomplished by simply forcing the fine particles of the agent together, with or without a binder, to form briquettes or pellets; or certain adhesives may be incorporated in the admixture which may then be slightly moistened and either compressed into briquettes or moulded into the desired shapes.

The efiervescence may be effected by introducing into the admixture any usual substance that will re-act with the acid bath to generate a disrupting gas, thus in effect blasting apart the aggregated materials. Such materials as powdered metal, carbonates, sulfides, etc. produce this result. I have found from the economic stand-point that sodium carbonate for producing carbon dioxide as a disrupting gas is highly satisfactory.

Various known materials may be used as the selective controlling agent, such substances as thiourea bodies, quiniline compounds and other compounds containing the nitrogen ring, various rubber accelerators, mercaptobenzothiazol, etc., serving the purpose satisfactorily.

Foamin a may be flour, soap-bark, powdered licorice or other colloidal materials having the property of producing foam on the pickle bath. The most effective substance appears to be either dried or liquid cellulose pulp waste. The cellulose pulp waste, being of a mucilage like character when moistened, is considered preferable since it will also act as the binder or adhesive for securing the particles of the admixture together.

In case greater bulk is required, some harmless substance may be used as a bulking agent, such substances as sugar, salt, sodium sulphate and other like substances being suitable.

To make up my agregated admixture I may use Pounds Diorthotolylthiourea 2 Sodium carb te 1 These ingredients are first pulverized and thoroughly mixed. They are then slightly moistened, 105

as with water, and firmly pressed into the form of pellets or briquettes, thus condensing the admixture to give it sumcient weight to immediately sink in the pickle bath.

Such a composition is immediately attacked by 110 Examine? the pickling bath with the liberation of carbondi-oxide gas, which acts as a blasting agent which quickly disintegrates the briquettes and disperses the selectively controlling agent throughout the bath.

A unit of these materials weighing 0.2 lb. is sufficient for treating a bath containing 100 lb. of 66 sulfuric acid and producing a bath that will remove rust and scale without seriously affecting the good metal. There will, however, be suificient attack on the metal to produce some obnoxious fumes. These fumes can be eliminated by adding 3 lb. e. g. of a foaming agent, such as evaporated cellulose pulp waste liquor, to the admixture before it has been weighted by aggregation.

The weighting of the materials by compressing the admixture into the unit so condenses its volume that a bulking agent may sometimes be required in order to produce sizeable units of the aggregated matter. The admixture may accordingly be augmented by the addition of anfillmg agent, for which purpose sodium chloride may be m. This subst n 'cularlydesirable since it will also act as an auxiliary gleaping agent-assistirtgthe'fifidby generating within the b'atKfiydrochloric acid. I have found that the addition of 5 1b. of sodium chloride to the above materials before they are unified produces satisfactory results.

In case it is not convenient to briquette the materials by condensing them and giving them weight by compression, I have found that good results can be obtained by moistening the assembled materials with suflicient water to form a putty-like mass which may be moulded into cakes of the desired size and then permitted to dry. These cakes may be of any desired weight, those ranging between 1 oz. and 1 1b., according to my experience, being the most practical.

After the pickling bath is made up using say: 200 gallons water, and 10 gallons 66 sulfuric acid I may add one or more units of my materials sufficient to make one pound, proportioned as follows:

Pounds Diorthotolylthiourea 2.0 Evaporated cellulose pulp waste liquor 3. Sodium chloride 5.0 Sodium carbonate (anhydrous) 0.5

This aggregate quickly dissolves and is effectively diffused in the acid solution, forming a bath ready for pickling steel. As the bath is re-inforced with acid from time to time to maintain its strength, additional amounts of my aggregate are added in proportion of about 1 lb. of aggregate to every 100 lb. of sulfuric acid employed.

It will be evident from the above description that my weighted aggregates afford not only a convenient and accurate means for doling out predetermined quantities, in relatively small amounts, of finely powdered materials for selectively controlling pickling baths, but the weighting of my admixture by aggregation causes it to sink immediately even though the bath is covered with foam and the admixture is immediately attacked by the bath and the elements thereof blasted apart by the disrupting gas and quickly and completely dispersed thereby through the bath in a wet condition. The results are that the exact quantities'of materials may be added at any time, the materials are uniformly and quickly placed in condition for functioning, no materials are lost through being removed with the work and no time is lost through delaying the pickling operations.

It will be apparent that various modifications of the invention are permissible, the scope of the invention being set forth in the appended claims.

Having now described my invention, I claim:

1. Means for use in a metal pickling bath for controlling the action thereof comprising a briquette of a density to sink in the bath and composed of compressed insoluble particles of a comminuted solid inhibiting material and a blasting agent incorporated therewith composed of an alkaline substance capable of reacting with the bath solution to produce a gas for blowing apart the briquette and dispersing its particles throughout the bath.

2. Means for use in a metal pickling bath for controlling the action thereof comprising a briquette of a density to sink in the bath and composed of compressed insoluble particles of a comminuted solid inhibiting material, a foaming agent, and a blasting agent comprising an alkaline substance capable of reacting with the bath to produce carbon dioxide gas for rapidly blowing apart the briquette and dispersing the particles thereof throughout the bath.

3. Means for use in a metal pickling bath for controlling the action thereof comprising a briquette of a density to sink in the bath and composed of compressed insoluble particles of a comminuted solid inhibiting material, a foaming agent, and sodium carbonate acting as a blasting agent reacted upon by the bath solution to produce a blasting gas to blow the briquette apart and disperse its particles throughout the bath.

4. Means for use in a metal pickling bath for controlling the action thereof comprising a briquette of a weight to sink in the bath and composed of insoluble particles of a comminuted solid inhibiting material, a foaming agent, and an agent capable of reacting with the bath to produce a gas for rapidly disintegrating the briquette in the bath.

- JAMES H. GRAVEIL. 

